1. Field of the Invention
The present invention relates to an ultrasound image of a cross-section of an organ of a human body, taken by ultrasonography, and more particularly, to a method of measuring fat content in a target organ by quantitatively assessing from the gray level distributions of pixels of an ultrasound visual image.
2. Description of the Related Art
Deposit of fat in a human organ may cause various complications, and results in the functional disorder of the organ. For instance, a fatty liver contains abnormally much fat, which, however, does not cause a pain and there is no particular subjective symptoms. Although a slight fatty liver can be found in a healthy person, there is a high probability that fat content in the liver increases abnormally and causes a complication or hepatocirrhosis. In this regard, diet life and obesity become social issues today, which draw much attention upon quantitative assessment of fat content in a human liver. As a result, methods of easily measuring fat content in a human organ at low cost have been continuously developed.
It is generally known that a fatty liver has a very close connection with fat content in a liver. Although various methods of quantitatively assessing fat content in a target organ have been continuously suggested or carried out, there is a growing need for a method of easily measuring fat content in a target organ of a human body at lower cost.
In order to assess fat content in a human organ, computed tomography (CT) is frequently used in obtaining a visual image of a cross-section of a human organ. CT is advantageous in that a visual image of high resolution can be obtained, and it is possible to precisely separate a ratio of fat content or other substances from a visual image irrespective of scanning techniques or ambient conditions. Nevertheless, it is very expensive to use CT, and further, there is much adverse criticism about the use of CT on a human body in that the human body is exposed to radioactive rays.
Meanwhile, fat content in a human organ is measured through hepatic biopsy. Hepatic biopsy is to analyze a tissue and substances of an organ taken off from a human body, e.g., a hepatic tissue, and can provide the most fundamental and exact diagnosis and inspection of hepatic disease. However, hepatic biopsy is very difficult to carry out and dangerous in terms of the invasiveness. Further, there is a strong tendency that hepatic biopsy is used when a patient does feel particular symptoms of disease. Therefore, in fact, hepatic biopsy is almost useless for preventive treatment.
On the other hand, ultrasonography is of wide use because it is possible to easily and cheaply obtain a visual image of a cross-section of a human body, including a cross-section of a belly, and diagnose and inspect the state of the human organ from the obtained visual image. Especially, ultrasonography is safe in that it does not use radioactive rays, and is not invasive. Despite these advantages, the quality of an ultrasound visual image is dependent greatly upon scanning techniques and ambient conditions, and the reflective characteristics and resolution of an object through which ultrasound wave passes are irregular. For these reasons, there is a higher probability that a person who diagnoses patient""s disease may put an arbitrary interpretation on a visual image taken by ultrasonography, thereby lowering the reliability of his/her diagnosis.
At the present time, the clinical determination of a fatty liver is largely divided into four levels, using ultrasonography: normal, mild, moderate, severe. However, an error range of the level of a fatty liver diagnosed by therapists who have experienced to diagnose patents"" diseases using ultrasonography, is within one level, and the probability that an error occurs is 20% at maximum.
Accordingly, there is a growing need for a method of quantitatively measuring fat content in a target organ, which uses ultrasonography that is simple and inexpensive to use, but is not affected by scanning techniques or ambient conditions. Although there are many methods of measuring fat content in a human organ only with ultrasonography, it is difficult to quantitatively measure fat content in an organ due to the distortion of image characteristics caused by an irregular gray level distribution and poor resolution of an ultrasound visual image. Also, the reliability of the result according to these methods is low.
To solve the above-described problems, it is an object of the present invention to provide a method of quantitatively assessing fat content in a target organ by measuring the gray level distribution of the target organ from an visual image taken by ultrasonography, and extracting a representative gray level.
Accordingly, to achieve an aspect of the above object, there is provided a method of quantitatively assessing fat content in a target organ from an ultrasound visual image, the method including obtaining an ultrasound visual image of the target organ, setting a target region in the obtained image, measuring a quantified representative gray level of the target region from a gray level distribution of pixels of the target region, and assessing fat content corresponding to the quantified representative gray level of the target region.
Here, the ultrasound visual image may be an image of a cross-section of a human belly, and the target region may include a human liver.
Measuring the representative gray level of the target region may include obtaining a distribution pattern of pixels of the target region, obtaining histogram distributions of the number of pixels with regard to gray levels of pixels of the target region, and determining the gray level of one histogram of the histogram distributions as the representative gray level. The representative gray level of the target region may be determined as a gray level of a histogram positioning at a point of inflection in the histogram distribution.
To achieve another aspect of the above object, there is provided a method of quantitatively assessing fat content in a target organ from an ultrasound visual image, the method including obtaining an ultrasound visual image of the target organ, setting a target region and comparative regions in the obtained image, measuring a representative gray level of the target region from a gray level distribution of pixels of the target region, measuring representative gray levels of the comparative regions from the gray level distributions of pixels of the comparative regions, quantifying the representative gray level of the target region as relative values as compared with the representative gray levels of the comparative regions, and assessing fat content corresponding to the quantified representative gray level of the target region.
Measuring the representative gray levels of the comparative region may include setting a path across each comparative region, obtaining a pixel distribution pattern of gray levels along the path, obtaining a distribution graph of gray levels of pixels along the path, and calculating an average of gray levels corresponding to maximum points in the distribution graph of the gray levels, and determining the average as the representative gray level of the comparative region.
Otherwise, measuring the representative gray level of the comparative region may include setting a path across each comparative region, obtaining a pixel distribution pattern of gray levels along the path, obtaining a distribution graph of gray levels of the pixels along the path, and calculating an average of gray levels corresponding to minimum points in the distribution graph of the gray levels, and determining the average as the representative gray level of the comparative region.
Otherwise, measuring the representative gray level of the comparative region may include setting a path across the comparative region, obtaining a pixel distribution pattern along the path, obtaining a histogram distribution of the number of pixels with regard to gray levels of the pixels, and calculating an average of some gray levels from the histogram distributions, and determining the average as the representative gray level of the comparative region.
Assessing fat content in the target organ may include collecting samples of ultrasound visual images, measuring quantified representative gray levels of the samples, and actual fat contents, obtaining a proportional function with regard to the quantified representative gray levels of the samples and the actual fat contents, and assessing fat content corresponding to the quantified representative gray level of the target region, using the proportional function.
According to the present invention, fat content in a human organ can be effectively and reliably measured from an ultrasound visual image thereof at low cost. A method of quantitatively assessing fat content in a human organ from an ultrasound visual image, according to the present invention, is very effective and reliable. Further, this method provides safe quantitative assessment of fat content at low cost.